My favorite Cinderella Story, Michael Davis, Shoot 'Em Up, went into New Line Cinema to pitch the script, ended up sharing some animated storyboard footage he'd put together to work out action scenes, walked out of meeting project approved and signed on as director (story from interview on dvd, also mentioned on
wikipedia). Just now looked him up on
imdb, discovered Davis already deeply savvy about directing. He'd already practiced, practiced, practiced. So this Cinderella was no newbie.
My understanding, could be wrong, we have True Romance because Tarantino so unhappy with what Stone did with Natural Born Killers. So if a director messes up your work, you might just end up with two great scripts out of it.
What you do control, entirely, are the words. Write your script so distilled and precise that any person reading it, or at least most folks reading it, will see it precisely as you intended. Good luck, Matti!